Physiology 1- body fluid compartments

Question 1

What is osmolarity?

Answer 1

concentration of osmotically active particles present in a solution

Question 2

What are the units for osmolarity?

Answer 2

osmol/l (mosmol/l)

Question 3

What 2 factors need to be known in order to calculate osmolarity?

Answer 3

the molar concentration of the solution; number of osmotically active particles present

Question 4

What is the difference between osmolality and osmolarity?

Answer 4

osmolality has units of osmol/kg whereas osmolarity has

Question 5

What is the osmolarity of body fluids?

Answer 5

around 300mosmol/l

Question 6

What is tonicity?

Answer 6

the effect a solution has on cell volume

Question 7

What are the 3 types of tonicity of a solution?

Answer 7

hypo-; hyper-; iso-

Question 8

What does tonicity take into accoutn in addition to osmolarity?

Answer 8

the ability of a solute to cross the cell membrane

Question 9

What 2 compartments does total body water exist as?

Answer 9

ICF and ECF

Question 10

What makes up ECF?

Answer 10

plasma; interstitial fluid; llymph and transcellular flui

Question 11

Give examples of transcellular fluid?

Answer 11

pleural fluid and CSF

Question 12

How can the vlume of body fluid compartments be measured?

Answer 12

tracers

Question 13

What is the equation for distribution volume when using a tracer?

Answer 13

distribution volume = Qx (known quantity of tracer)/ concentration of X in compartment

Question 14

What is insensible fluid loss?

Answer 14

loss of water that the body has no physiological control over

Question 15

How are the kidneys involved in water balance?

Answer 15

water balance is maintained by increased water ingestion; decreased excretion of water by the kdineys alone is insufficient to maintain water balance

Question 16

Why can decreased excretion of water by the kidneys not maintain water balance?

Answer 16

some water always has to be excreted by the kdineys as some metabolic waste products can only be excreted in solution

Question 17

What is the concentration of sodium in the ECF like in comparison to ICF?

Answer 17

higher in ECF (we evolved from fish, our internalised environment (ECF) is like the sea-salty!)

Question 18

What are the main ions in the ECF?

Answer 18

Na; Cl and bicarb

Question 19

What are the main ions in the ICF?

Answer 19

K; Mg and negativley charged proteins

Question 20

Why is the regulation of fluid and electrolyte balance tightly intertwined?

Answer 20

changes in solute concentration lead to immediate changes in water distribution

Question 21

What is fluid shift?

Answer 21

movement of water between the ICF and ECF in response to an osmotic gradient

Question 22

What happens if the osmotic concentration of the ECF increases>

Answer 22

water shifts into ECF from ICF to restore osmotic equilibrium

Question 23

What are the 3 challenges to fluid homeostasis?

Answer 23

gain or loss of water; gain or loss of NaCl; gain or loss of isotonic fluid

Question 24

What happens if there is a gain or loss of water?

Answer 24

there is a similar change in ICF and ECF volumes; both increase or decrease (osmotic equilibrium is maintained)

Question 25

What happens if there is gain or loss of NaCl?

Answer 25

PM is relatively impermeable to NaCl so water compensates to maintain osmotic equilibrium

Question 26

What happens if there is a gain or loss of isotonic fluid?

Answer 26

there is no change in fluid osmolarity, there is a change in ECF volume only

Question 27

How do the kidneys fit into fluid homeostasis?

Answer 27

kidney alters composition and volume of ECF

Question 28

Why is maintaining electrlyte balance important?

Answer 28

total electrolye concentrations can directly affect water balance; the concentrations of indiviual electrolytes can affect cell function

Question 29

What makes up more than 90% of the osmotic concentration of the ECF?

Answer 29

sodium salts

Question 30

What happens if there is a decrease in potassium plasma concentration?

Answer 30

muscle weakness–paralysis; cardiac irregularities–cardiac arrest

Question 31

Why is regulation of ECF volume important?

Answer 31

long-term regulation of BP